C Program to implement the midpoint circle drawing algorithm

#include <graphics.h>
#include <conio.h>
#include <math.h>
#include <stdio.h>
 
#define PI 3.14
 
float startangle,endangle;
int x,y;
 
int Can_draw( float theta )
{
if( theta >= startangle && theta<= endangle )
return 1;
return 0;
}
 
void Circlepoints(int x,int y,int xc,int yc)
{
float theta;
theta = atan( (float)y/x );
theta = theta * (180/M_PI);
 
if( Can_draw(theta))
putpixel(xc+x,yc-y,WHITE);
if( Can_draw(360-theta))
putpixel(xc+x,yc+y,WHITE);
 
if( Can_draw(90-theta))
putpixel(xc+y,yc-x,WHITE);
if( Can_draw(270+theta))
putpixel(xc+y,yc+x,WHITE);
 
if( Can_draw(180-theta))
putpixel(xc-x,yc-y,WHITE);
if( Can_draw(180+theta))
putpixel(xc-x,yc+y,WHITE);
 
if( Can_draw(90+theta))
putpixel(xc-y,yc-x,WHITE);
if( Can_draw(270-theta))
putpixel(xc-y,yc+x,WHITE);
}
 
void MidPointcircle(int xc,int yc,int rad)
{
float d = (5/4.0) - rad;
x=0,y=rad;
 
while(y>x)
{
if(d<0) 
d += 2*x+3;
else 	
d+=(2*x)-(2*y)+5,y--;
x++;
Circlepoints(x,y,xc,yc);
delay(90);
}
}
void main()
{
int gd=DETECT,gm;
int radius,xc,yc,choice,temp;
float xstart,ystart,xend,yend;
initgraph(&gd,&gm,"..\\bgi");
do
{
clrscr();
cleardevice();
printf("\n Enter your choice\n");
printf("\n 1.Draw a Circle\n 2.Draw a Sector\n 3.Draw an Arc\n 4.Exit\n");
scanf("%d",&choice);
switch(choice)
{
case 1: printf("\n Enter the center:");
scanf("%d %d",&xc,&yc);
printf("\n Enter the radius:");
scanf("%d",&radius);
cleardevice();
startangle=0,endangle=360;
MidPointcircle(xc,yc,radius);
getch();
break;
 
case 2: printf("\n Enter the center:");
scanf("%d %d",&xc,&yc);
printf("\n Enter the radius:");
scanf("%d",&radius);
printf("\n Enter the startangle:");
scanf("%f",&startangle);
printf("\n Enter the endangle:");
scanf("%f",&endangle);
cleardevice();
if(startangle>endangle)
{
temp=startangle;
startangle=endangle;
endangle=temp;
}
MidPointcircle(xc,yc,radius);
xstart=xc+radius*cos(PI/180*startangle);
ystart=yc-radius*sin(PI/180*startangle);
xend=xc+radius*cos(PI/180*endangle);
yend=yc-radius*sin(PI/180*endangle);
line(xc,yc,xstart,ystart);
line(xc,yc,xend,yend);
getch();
break;
 
case 3: printf("\n Enter the center:");
scanf("%d %d",&xc,&yc);
printf("\n Enter the radius:");
scanf("%d",&radius);
printf("\n Enter the startangle:");
scanf("%f",&startangle);
printf("\n Enter the endangle:");
scanf("%f",&endangle);
cleardevice();
if(startangle>endangle)
{
temp=startangle;
startangle=endangle;
endangle=temp;
}
MidPointcircle(xc,yc,radius);
getch();
break;
 
case 4:  closegraph();
}
}while(choice!=4);
}